A sheet of glass can be bent for a particular application then quenched to both increase its mechanical strength and improve its breakage characteristics.
In many conventional flat glass bending and tempering operations, a sheet of glass to be bent and tempered is heated in a glass heating furnace to its deformation point of about 1200.degree. F. to 1300.degree. F. The glass sheet is then removed from the furnace along a roller conveyor having conveyor rolls to a bending station for bending of the heated glass sheet to the desired shape. After the glass is bent at the bending station, the bent glass sheet while still soft is conveyed along the roller conveyor to a quenching station, and some change of shape is bound to occur.
At the quenching station cooling gas is rapidly applied to the now bent heated flat glass sheet. Rapid cooling sets up high compressive forces near the surfaces of the glass sheet which give it desired strength and breakage characteristics.
It is important that the quenching step takes place soon after the glass sheet leaves the furnace. Premature cooling has been known to take place before the bending station adversely affecting the bending and tempering character of the glass sheet.
U.S. Pat. Nos. 4,092,141 to Frank et al and 3,846,104 to Seymour disclose methods and apparatus for handling glass sheets for shaping and cooling. Hot glass sheets are lifted into engagement with a vacuum shaping mold and held there by vacuum as the lifting mechanism retracts. A tempering ring is brought into position and the glass is released to deposit the bent glass sheet on the ring for movement to a cooling station. This method requires complicated equipment including a vacuum source and also requires separate bending and quenching stations.
U.S. Pat. No. 2,223,124 to Owen discloses a method of bending and case hardening a glass sheet on a roller runway. Rolls on the roller runway sag to bend the glass sheet thereon and blasts of air are applied to the bent glass sheet. The glass sheet remains in contact with the roller runway throughout the bending and case hardening and is subjected to the heat retained in the rollers from repetitive operation of the apparatus.